Car wont shift into any position

You have to locate where the park ignition switch is located. Some are on the transmission and some are in the column under the dash. It probably got moved.

you can shift it at transmission by hand to neutral or park and have someone inside start the car and you manually put in gear under hood and drive it to shop or garage, wherever

Do you have your foot on the brake when trying?

It sounds like the linkage at the transmission has come loose. Have someone get inside and move the shift lever from gear to gear so you can see where the linkage is on your transmission. You'll have to climb under ypou truck to see this, on the drivers side. check to see that all the bolts are tight. Your switch that allows you truck to start in Park or Neutral is located there.

On the 1995 Jimmy, the shift cable can come loose on the mount on the side of the transmission where the cable meets the trans. When it slips, the alignment goes off and causes the driver to not be able to put the trans into park. If you take a long stick you can push the shift arm on the trans to the park position and your trans will go into park.....what you (and I) really need to know is how to take the shift cable mount apart and reset it.

Ok now heres the question???? Will gear shift move at all? I mean can you actually get it into drive or reverse? If you cant move the shifter than it is most likely the brake switch located at the top of the brake pedal. They have been know for this problem. But if you can move shifter and just wont go then your probably looking at linkage problem or transmission problem.

Shift linkage bushings under the air filter box are probably gone.
http://www.boogerracing.com/boogerbushings.html

it sounds like your gearshift cable is broken..if you can jack up vehicle and support it safely,get someone to move shifter and look on driver's side of transmission and see if linkage is moving on trans..linkage is up near top of trans..i have seen this problem before

set your parking brake, insert your key into the shift interlock, located next to your shifter, push all the way in, move your gear shifter to neutral, remove key, start car, release parking brake, drive away, have it serviced ASAP

There should be a button somewhere around the gear shift. The button is there so that you can shift out of park when the engine is not running and it wont be obvious that this is what it is for. You will probably have to press it with a screwdriver. When it is fully depressed the gear shift should move.